1. Field of the Invention
The present invention relates to improvements in recovering valuable by-products from mixed salt-rich aqueous solutions and, more particularly, to the production of potassium sulfate and sodium sulfate from sea water brines, natural bitterns or the like.
2. Description of the Prior Art
There are numerous solar salt facilities around the world operating under a wide variety of plant sizes and operating conditions. Such facilities, however, have not been expanded to recover by-product salts from their residual brines because of the complexity of the salts contained therein and the comparatively large expenditures of capital equipment that would be necessitated under current technology to recover significant quantities of valuable by-product salts. Additionally, by-product recovery is exacerbated by the fact that potassium salt concentrations in residual brines is low and such potassium usually crystallizes in the form of various double salts mixed with magnesium sulfate and sodium chloride.
One system which discloses a variety of processing techniques for the recovery of valuable potassium salts is U.S. Pat. No. 3,528,767. This patent describes the solar evaporation of bitterns with sequential segregation of the precipitating salts so that various potash-rich fractions may be isolated and processed separately. The processing includes suitable crushing and classification followed by a flotation separation. When it is desired to produce potassium sulfate as an end-product, generally the potassium salts are converted to schoenite which is subsequently converted with hot water or aqueous potassium chloride solutions to yield the potassium sulfate product. A problem with the aforementioned processing is that the salts which are precipitated in the evaporation ponds do not provide any simple method or opportunity for producing sodium sulfate.